Comparative Evaluation of Toleration to Heating and Hypoxia of Three Kinds of Salmonids

Abstract

This study was conducted to evaluate the critical thermal maximum (CTMax), the routine metabolism rate (MO2) and the limiting oxygen saturation (LOS) of three salmonids with four different body weights ranging from 16 g to 131 g. The CTMax was estimated at three different heating rates including 0.5°C min−1, 1°C h−1 and 2°C d−1. Results showed that the CTMax of maple trout (Oncorhynchus mykiss) was the highest, which was followed by steelhead trout (O. mykiss) and Atlantic salmon (Salmon salar). The CTMax of the salmonid fish decreased with the increment of body weight, and was significantly influenced by the heating rate. The MO2 of the salmonid fish increased with the increment of temperature, and decreased with the increment of body weight. Suffocation points of the fish decreased with increasing body weight and temperature. Steelhead trout was more tolerant to hypoxia than maple trout and Atlantic salmon, while the MO2 of Atlantic salmon was the highest among these three salmonids. The LOS of the fish generally had a positive trend with temperature and body weight, and the LOS of steelhead trout was significantly lower than that of maple trout and Atlantic salmon. In conclusion, maple trout was the most tolerant kind to high temperature, while steelhead trout was the most tolerant to hypoxia among three kinds of salmonids. Moreover, the abilities to tolerate higher temperature of three salmonids were affected by their body weight and the heating rate, while the abilities to tolerate hypoxia were influenced by their body weight and the water temperature.